This invention relates to universal joints in general and more specifically to universal joint yokes.
Yoke members of universal joint assemblies are typically made of forged steel because of its strength. Particularly in heavy duty models, strength and torsional stiffness are critical, as is overall weight. Forged steel is a proven reliable material which unfortunately is expensive because it requires extensive heat treating and processing.
With increasing energy costs, industry has attempted to reduce the cost of typically forged steel parts by substituting materials. Some exotic materials could be adequate substitutes, but their is also high. Some manufacturers have had limited success in substituting cast iron for forged steel. In the universal joint field, however, the successes have been limited to small yokes which have not been subject to great loads, torsional forces, etc.
With heavy duty components, mere substitution of cast iron has been unacceptable because of its characteristics, specifically its lower fatigue strength. Cast materials are more sensitive to stress risers, which can appear at critical areas of a component.
It is for the above reasons that industry in general is moving more toward the use of exotic materials in place of forged steel for heavy duty torsional members.